Surrogacy is a practice in which a woman ( a surrogate mother ) bears a child for a couple unable to produce children; usually, because the wife is infertile or unable to carry a pregnancy to full term.
The surrogate mother is impregnated with the use of artificial insemination or through the implantation of the embryo produced by in vitro fertilization.

Pangaea was a large, irregular land mass which later broke up into various continents. It existed around Carboniferous period (some 345 million yeas back) or a little earlier.

Oral pills contain progrestins and estrogen which check ovulation; Combined pill, Mala D and Saheli.

(i) Blending is the mixing of two colours,but in this example red and white colours are appearing independently at cellular level. Thus, no blending of characters occurs in this case. Also, red and white colours reappear in F₂ - generation.
(ii) This phenomenon is known as incomplete dominance.

(i) It is a non-steroidal preparation.
(ii) It is a 'once' a week' pill.
(iii) It has high contraceptive value.
(iv) It has fewer side effects than other oral contraceptives.

Advantage
1. Since cleistogamous flowers are autogamous, there is an assured seed-set.
Disadvantage
1. Continued self-pollination leads to inbreeding depression.

(a) A meiocyte is diploid cell, while a gamete is haploid.
(b) A whiptail lizard develops from the female gamete, without fertilisation; hence it is parthenognetic.

(a) Parthenocarpy: The formation of fruit without the act of fertilization is called parthenocarpy and the fruits so developed are called as parthenocarpic fruits. These fruits are seedless. e.g., banana. While apomixis is a special type of sexual reproduction which does not involve meiosis and syngamy. In fact it is a form of asexual reproduction that mimics the sexual reproduction in which the seeds are produced without fertilization
(b) Apomictic seeds can be produced by any of the following methods.
(i) Apospory: It is the formation of diploid embryo sac directly from a cell of nucellus
(ii) Diplospory or generative apospory: It is the formation of diploid embryo sac from the megaspore mother cell without meiosis.
The diploid egg of the diploid embryo sac develops into embryo without syngamy i.e., parthenogenetically.
Apogamy : The synergids or antipodals of the diploid embryo sac may develop into embryo parthenogenetically.

Spermatogenesis is under the control of endocrine hormones. In human male reproductive system, spermatogenesis starts at the age of puberty due to significant increase in the secretion of gonadotropin-releasing hormone by hypothalmus. The increased level of GnRH then acts on the anterior pituitary gland and stimulates secretion of the two gonadotropins : Luteinising hormone (LH) and follicle stimulating hormone (FSH). LH acts on leydig cells and stimulates synthesis and secretion of androgens, like testosterone which stimulates spermatogenesis. FSH acts on the sertoli cells and stimulates secretion of some factors which help in the process of spermiogenesis. Excess of testosterone inhibits the secretion of LHP and GnRH. A glycoprotein called inhibin supresses FSH synthesis. Thus normal release of testosteron is under negative feed back control.

(a) Salmonella typhi.
(b) Widal test.
(c) The pathogen enters the human body through contaminated food and water.
Symptoms 
Symptoms of typhoid include:
(i) sustained high fever (39-40 ^oC)
(ii) loss of appetite 
(iii) stomach pain 
(iv) headache and weakness 
(v) intestinal perforation in severe cases may cause death.
Intestine gets affected in severe cases.

a) Inbreeding depression can be overcome by outcrossing.
(b) (i) Inbreeding is necessary to evolve purelines in any animal, as it increases homozygosity.
(ii) Inbreeding exposes the harmful recessive alleles, which become eliminated by selection.
(iii) It helps in accumulation of superior genes and elimination of the less desirable ones.
(c)Hisardale, a breed of sheep.

The lac operon consists of
(i) three structural genes (z,y and a) which code for \(\beta \) -galactosidase, permease and transacetylase, respectively.
(ii) an operator; which controls the structural genes as a unit.
(iii) a regulatory gene ti.e., inhibitor gene) and
(iv) a promoter, where the RNA polymerase binds for transcription.
The regulatory gene codes for the repressor protein, all the time (constitutively): the repressor binds to the operator to inactivate the operon.
 Lactose enters the cell with the help of permease and the active form of lactose binds to the repressor and prevents it from binding to the operator.
This allows RNA polymerase an access to the promoter and transcription continues, i.e. lac operon is activated.

1.The gene for haemophilia is present on the X chromosome, i.e. sex-linked.
2.The disorder is due to a recessive mutant allele; hence a female with XX sex chromosomes, must be homozygous to produce the disease.
3.She must receive one of the defective alleles from her haemophilic father and the other X-chromosome with the defective allele from her mother; who is also haemophilic or at least a carrier (heterozygous for the trait, XXh).
4.The cross is as follows.

(i) Ascariasis
Cause. It is caused by Ascaris lumbricoides.(round worm).
Symptoms.Its symptoms include:
(a) Blockage of intestinal passage,
(b)Anaemia,
(c)Abdominal/muscular pain,
(d)Internal bleeding,
(e)Nausea and headache.
Modes of transmission. Infection is through contaminated vegetables, fruits and water as eggs of parasite excreted by the infected persons contaminate soil, plants and water
(ii) Filariasis/Elephantiasis
Cause. It is caused by wuchereria bancrofti and wuchereria malayi(filarial worms)
They normally cause inflammation of the organs in which they live for many years.
They normally affect the lymph vessels of the lower limbs (causing them to swell like that of an elephant, hence called elephantiasis).
Genital organs may also be affected leading to gross deformation.
Modes of transmission. The female culex mosquito is the vector.
(iii)Ringworms
Cause. These are caused by fungi like microsporum, Epidermophyton and Trichophyton
Symptoms. The symptoms include
(i) dry scaly lesions on skins, nails and scalp.
(ii)lesions are accompanied by itching.
Modes of transmission. Ringworms are generally acquired from soil or by direct contact with the contaminated articles used by the infected persons.

Kinds of selections:
1. Stabilising selection
2. Directional selection
3. Disruptive selection.